Food irradiation reactor



May 2, 1961 c. F. I EYsE ET AL FooD IRRADIATION REAc'ToR '7 Sheets-Sheet 1 Filed June 27, 1957 May Z, 1961 c. F. LEYsE x-:TAL 2,982,710

FOOD IRRADIATION REACTOR Filed June27, 1957 7 Sheets-Sheet 2 Inventors afl F Leg/5e Glen E. Puff-7U- May 2, 1961 c. F. LEYsE ETAL Foon IRRADIATION REAcToR 7 Sheets-Sheet' 3 Filed June 27, 1957 Ifz V617, 0115 Carl f Le Glen E May 2, 1961 c. F. LEYsE ETAL 2,982,710

4 FOOD IRRADIATION REACTOR Filed June 27, 1957 `"i Sheets-Sheet Bry" May 2, 1961 c. F. LEYsE ET AL Foon IRRADIATION REAcToR 7 Sheets-Sheet 5 Filed June 27, 1957 s mw@ am; yo neu WLP @FFW 1n ww 66% May 2, 1961 c. F. LEYSE ETAL Foon IRRADIATION REAcrToR 7 Sheets-Sheet 6 /60 1 E E C Inventors Carl E' Legs@ Filed June 27, 1957 May 2, 1961 c. F. LEYsE ETAL 2,982,710

Fo'on IRRADIATION REAcToR Filed June 27, 1957 7 Sheets-Sheet '7 F1' E ll /Jmf 'In venters afl E Legs@ @Len E. Putnam.

2,982,710 Foon IRRADIATION RnAlcron Fried time 27, 1957, ser. No. 668,588 1 claim. v(Cl. 20e-193.2)

This invention relates to `an ionizing energy source States Patent l C for irradiating selected materials and more particularly to a device and process comprising a neutronic reactor for producing gamma rays usable for irradiating foodstuifs.

It is well known that ionizing radiations possess bactericidal properties which are particularly useful in the preservation of foods, sterilization of medical products and other applications. The advent of greater technology in the lield of high intensity radiation sources has added radiation sterilization to the hitherto four basic methods of food preservation, namely heat processing, dehydration, refrigeration, and the use of chemicals. To adequately preserve and stcrilize materials such as foodstulfs and medical products by this method, it is necessary to utilize ionizing radiations which possess suiiicient energy to penetrate matter and are available in suicient intensities to produce the desired effects. Gamma rays, particularly those available from nuclear reactor systems, are readily adaptable for use as preserving sterilizing radiations. Y

There are essentially four different gamma sources from a nuclear reactor system and are: 1) prompt iisysion gammas released. in the iissioning reaction of the vreactor fuel, (2) f capture gammas released in the absorption of neutrons in poison materials within the reactor, (3) delayed fission product gammas released in the radioactive decay of materials formed by the nucleus split in the iissioning process, and (4) radioactive isotopes produced by the excess neutrons not necessary to sustain the chain reaction. Of these, the prompt and capture gammas are emitted practically instantaneous upon neutron absorption so that they cannot be removed for external f use. The delayed fission product gammas and the radioactive isotope gammas are available-subsequent to neutron absorption for a period of time dependent on the half-life of the particular materials; About 3% of reactor power appears as prompt gammas while l to 4% appear as capture gamma depending on the element in which the capture occurs. About 2.5% of the reactor power is displayed as delayed ssion product gammas and up to 2% appears as gamma `emitting radioactive isotopes produced from excess neutrons. The total gam- 'ma power available from a reactor theoretically approaches 12% of its total heat power; however, in most practical cases it is only about 1%. Of the available 1% perhaps 10% is finally absorbed in the material being irradiated.

It is therefore an object of this invention to provide a nuclear reactor system for supplying ionizing radiations for the preservation and sterilization of selected materials wherein optimum use is made of the energy radiationsproduced therein. A,

'This invention also relates to a nuclear reactor system for irradiatng foodstus and medical supplies wherein radiator shown in Figure 9;

.i 2,982,716 Y l vPatented MayZ, 1961- gamma radiation energies are produced by the absorp- `be absorbed in the iissionable material. A minimum of about .25 neutrons must be lost -by absorption in the core structure material and coolant. Approximately .25 neutrons leak out `of the entire system, mostly as fast neutrons and thus some .8 neutrons per ission are available for absorption in the emitter material. The .emitter material may be formed in a blanket around the reactor core in such a manner that the absorptioncharacteristics thereof will not affect the reactivity of the core itself.

It is thus .another object of this invenion to provide a` reactor system for irradiating food stuffs and medical supplies wherein the utilization of reactor power to form the ionizing radiations nas no substantial effect upon the reactivity of the reactor thereby providing a maximum range of variations without affecting theA stability of the reactor.

It is a third object of this invention to provide a reactor for use in a system for irradiating foodstuifs and medical supplies wherein a maximum number of excess neutrons are available for absorption in the emitter blanket to release gamma radiations.

Thesevand other objects are obtained by the novel construction, combination of materials, and arrangement of said materials hereinafter described and shown in the accompanying drawings in which:

yFigure 1 is a schematic drawing of the reactor system showing the reactor and its relationship with the cooling system and the food irradiation facilities;

Figure 2 is a vertical sectional view of the neutronic reactor showing the internal components therein;

Figure 3 is a horizontal sectional View taken along the line 3 3 of Figure 2 showing the arrangement of the control rods for the reactor; y

Figure 4 is a horizontal sectional view taken along the line 4 4 of Figure 2 showing the arrangement of the active core Within the reactor; Y Figure 5 is a vertical sectional View of one ofthe drumtype irradiation facilities in a reactor system;

Figure 6 is a horizontal plan view of one of the irradiation drums Figure 7 is a Vertical sectional view taken along the line 7-7 of the irradiation drum shown in Figure 6;

Figure 8 is a horizontal sectional View taken along the line 8-'8 of Figure 7;

Figure 9 is an elevation view sectioned in part of one of the slab irradiators;

Figure 10 is an isometric view of part of the slab ir- Figure ll is an elevation view of the other slab irradiator; Y

Figure 12 is a vertical section view of the portion circled and denoted 12 in Figure 1l; and

Figure 13 is a vertical section View of the portion encircled and denoted y11' in Figure 11.

The irradiation facility described in detail hereinbelow and illustrated in the attached drawings hasbeen designed 'for the express purpose of irradiating foodstuffs and r d I...

indium sulphate,` indium chloride or nitrate, an

indium solution system including the reactor blanket and the gamma irradiators, and primary and auxiliary cooling water systems for removal of reactor heat. The reactor core is preferably of cylindrical shape having its length substantially greater than its diameter. This arrangement maximizes neutron leakage for absorption by the indium.

As shown in Figure 2, the reactor is disposed within a `tank"22 formed by a concrete biological shield ,'24 and is submerged byia water coolant 26 therein. The re- 'actor 20 comprises an elongated tubular pressure vessel 28 housing the active portion 30 and control elements 32. Thereactor vessel 28 is an assembly'of three `separate units,v namely an upper tank 34, a center tank `36, anda lower tank assembly 38. The upper tank 34 is a, hollow cylinderhaving a cover dome at its upper end with two a o e t and lowerl grids `68 and 70, ller blocks 72, bolts 76, plates 80 and spacer blocl 82 are all fabricated of aluminum to reduce the parasitic capture of thermal neutrons within the active portion 30. The ller blocks 72 are outlets A40 for the passage of coolant therethrough. The p center tank 36 is a tubular element fabricated of a thermal neutron'` permeable material such asfaluminum and has an inside flange n42 around its lower end which supports the core structure 30. The lower tank assembly 38 conssts of two concentric tubes, anpinner one 44 andan 'outer one 46. A pair of inlets 48 and a pair of outlets 50 are disposed near the upper end of the outer tube 46 with a bafe ring 51 positioned in the interstice between the Ainner tube 44 and outertube 46 to form separate chambers 52 and 54 communicating with the 'inlets 48 c and outlets 50, respectively. Orifices 56 are formed ,near the lower end of the inner tube 44 forming passages for coolant to ilow between the chamber 52 and the inside of the tube 44. The center tank 36 and the lowertank 38 are joined by an annular plate 58 to which both are welded. The lower end of the lower tank 38 is welded to annular plate 60 which supports the pressure vessel 28 on the platform 62 over a lead shot shield plug 64.

In one particular construction of a neutronic reactor used `to illustrate the present invention throughout this description, the pressure vessel 28 is approximately 12 feet long, the center tank 36 surroundingA the active portion being a 50"` long tubular shell having an 18.5" O.D. 17.75" I D. uThe upper and lower tanks 34 and 38, respectively, are constructed of stainless steel to resist corrosion by the coolant fluids. The inner tube 44 of the lower tank assembly 38 has an inner diameter of-19.250", the outer diameter of the outer tube 46 being 32.25". REACTOR CORE ASSEMBLY The reactor core assembly or` active portion 30 consists of -fuel assemblies 66 supported by upper and lower grids 68 land 70, respectively, control rods 32, an assembly of thermal Vneutron permeable ller blocks 72 `(Figure 4) and rod guides 74. The fuel assemblies 66 are arranged in what may be called a staggered square load- ,ing with the filler blocks 72 filling the space between the center tank 36 of the pressure vessel 28 and the fuel assemblies 66. It is to be understood that a maximum neutron flux leakage from the active portion 30 `ofpthe reactor is desirable and is accomplishedby using a fuel assembly array geometrically shaped to have a substantially large surface to volume ratio. The length of the active portion 30should be greater than its diameter and ideally` over two times as great. `Thefuel -assemblies 66 are supported by the lower grid 70 which rests upon the flange 42 at the bottom end of the center tank 36. The fuel assemblies 66 are held in place at their upper end by the upper grid 68 which is supported around its periphery by the iiller blocks 72 and boltedthereto. The filler blocks 72 are held in position bylmeans of bolts 76 extending downward therethrough and threadedly engaging the center-tank"flange` 42.- A gap 78 between the pressure vessel 28 and the ller blocks 72 serves as a :with spacer blocks 82, `are'pdisposed withinthe core 30 to form'the -control rod guides 74. t

1:51a,thepartiularreactort-describ d herein, the `upper passage for the flow oftcoolant. Flat plates 80, together approximately 38.750 long and are assembled so. that their outside surfaces describe a 17 5A" diameter cylinder which fits into the center tank 36 with a l/" annulus therebetween for the flow of coolant. The upper and lower grids 68 and 70 are constructed so that 24 fuel assemblies 66 are situated in the core 30 in the described array with a center-to-center distance of 2.50" between adjacent assemblies. However, the center-to-center distance between fuel assemblies on either side of the rod guides 74 is 3.1875", the rod guides measuring .6015" thick overall and plates 80 being 0.102" thick.`

FUEL ASSEMBLIES The fuellassemblies 66 inthe active portion 30 are of the flat plate type construction similar tothe fuel assemblies disclosed in the co-pending application of Eugene P. Wigner, S.N. 314,595, filed October 14, 1952, now Patent No. 2,831,806, issued April 22, 1958. The fuel assemblies `66` of this invention differ therefrom only in that the fuel plates 84 are flat rather than curved, end boxes 86 (Figure 2) both have rectangular cross sections land the assemblies are not enclosed in a lcovering as shown in the co-pending referenced application. Plates 84 of material fissionable by thermal neutrons are clad with a corrosion resistant material and secured to side plates88. The, side pieces 88 have longitudinal grooves 89 and extend in either directionbeyond the length of the fuel plates 84 where they are connected to the rectangular cross section end boxes 86 which secure them in the upper and lower grids 68` and 70, respectively. In the construction of the particular neutronic reactor illustrating the present invention, the plates 84 are fabricated of an aluminum-uranium alloy of approximately 31.6 weight percent uranium enriched between 90 and 95%, each plate measuring .050" thick, 2.372" wideand 37" long and clad with. 15 mil aluminum. The side pieces 88 `are .098 thick aluminum plates having 16 longitudinal grooves to receive 16 fuel plates 84 spaced 0.106" apart for the llow of coolant therebetween. The width of the, side pieces is 2.460" andthe grooves are ,so cut that the finished fuel assembly 66 has a square cross section, each side measuring 2.460. With the above construction of the'fuel assemblies 66 the metal-to-coolant ratio of an individual assembly is.0.58 fand the overall metal-tocoolant ratio for the core is about 0.7 including the control rods which will be hereinafter described. t

coNrnor. noos As seen in Figure 4, the control rods 32 consist of a cruciform cross section shim `rod 90, four plate-type shim pods 92 and two cylindrical regulating rods 94. Each of the shim rods 90 `and 92 is constructed having a thermalneutron absorbent core enclosed in a non-corrosive, thermal-neutron. permeable cladding 95a at the upper end, and a 'solid rod of` the cladding material at its lower end so that -it will be transparent to the fission reaction when it is in itsraised` positionand will actas a poison tothe reaction when in its lower position. 4Each of the regulating rods 94 isa solid bar of thermal-neutron permeable material at the lower end with van airfilled thermal-neutron absorbent tube `clad with a non-corrosive, thermal-neutron permeable material at the upper end.

, `Inthe particular reactor described, the shimrod 9'0 has a cruciform cross section measuring 2.5fromthe longitudinal axis of the rod to the blade tips. The upper part of the rod 90 is formed of .062" thick `cadmium which `is sandwiched between .102 thick aluminum sheets, .the assembly being fusion welded to form a watertight plate assembly. The lower end of the shim rod 90 `isa cruciform cross sectioned rod of solid aluminum. The plate `shim rods `91,2 are similarly fabricatedlof .062"

assente -rods 90 and 92 are 36 long while the lower sections which are entirely aluminum are approximately 47 long. The upper section of the regulating lrod 94 is an aluminum clad cadmium tube having a 1.375 QD., .062 thick and approximately 24" long, the cladding being .0625" thick. The lower section is a solid beryllium rod Each of the'shm rods 90 and 92 and the regulating rods 94 have extensions 96 (Figure 2) at their lower end extending through shock absorber housings 98 and channels 100 through the 'lead shield plug 64 to a space' 102 below the reactor which houses the control rod driving mechanism. Each ofthe control rods 32 has its own motor 104 drivingly connected thereto through suitable clutch and gear means. Each of the rods is separately controllable and the shim rods 190 and 92 are responsive to a power surge of the reactor so that they will drop under the force of gravity so that the cadmium sections will be inserted into the active portion 30A of the reactor. The clutch and gear means and the separate control means are not shown as they are well known in the art of reactor engineering and form no part of the presently claimed invention. v

IRRADIATION BLNKET i Surrounding the pressure vessel l28 around its active portion 30 is an annular container or blanket 106 in which ows a lluid capable of emitting gamma rays upon the absorption of neutrons emanating from Vthe activeV portion 30. The blanket 106 is formed of two semicircular tanks 107 held together by piano-type hinges 108 (Figure 4), each tank 107 having its ends tapered away from the reactor vessel 28 to facilitate the ilow of coolant therearound. The blanket fluid is introduced into each of the tanks 107 through pipes 110 and is removed therefrom by means of pipes 112. The blanket 106 is supported by footings 114 maintaining it at a spaced relationship above the annular plate 58. The blanket 106 isl also spaced from the pressure vessel 28 by means of spacer wires 116 so that coolant may flow therebetween.`

In the particular reactor described, the tanks 107 each have 1A" stainless-steel walls forming a 4" wide space for containing the iluid so that the total volume or the tanks is approximately 5.3 cubic feet. An aqueous indium sulphate solution of up to 600 gramsper liter concentration flows through the tanks 106 and is used to irradiate the selected materials as hereinafter described.

Surrounding the indium blanket and separated from it by spacer wires 118 is a thermal shield 120 formed'of a neutron absorbing material which serves to reduce the gamma heat dissipated in the reactor water coolant pool 26 and concrete shield 24 by absorbing the neutrons escaping the blanket 106. A 3" thick 48 long stainless clad carbon steel tube with a 1A" water annulus between the tube and the blanket is used in the particular reactor described, serving to reduce the heat of the shielding pool and concrete biological shield.

COOLING SYSTEMS v The schematic flow diagram of the cooling systems for the reactor is shown in Figure lof the drawings. The reactor heat is removed from ythe active portion 30 with in the pressure vessel 28 by means of la primary coolant loop 124. The primary coolant is drawn through the reactor from the chamber 52 through orifices 56 and upward through the hollow fuel assemblies 66 and the upper shell 34 of the pressure vessel 28 to the coolant outlets 40. The coolantis transmitted to the heat exchanger 126 l'by pipe means 128 where the heat is extracted anddeposited to the'atmosphere in a manner well known to the art. The coolant is withdrawn from the heat exchanger 126.through pipe means v130 to the suc- 6 tion end of primary coolant pump 132 and is returned to the reactor by means of pipe means 134 Vto coolant inlet 48. A second cooling pump 136 is connected parallel to the primary coolant pump 132 to operate dur ing shutdown periods of the reactor. The primary coolant system for the particular reactor described is designed to keep the temperature of the hottest fuel plate surface within the core below approximately 366 F. A M60 gallon per minute device is used as the primary pump 132 to circulate the water coolant at a velocity of 7.5' per second through the core =at `a pressure of approximately 150 p.s.i.g. The shutdown pump 136 has a capacity of approximately 50y gallons per minute which is adequate to dissipate heat liberated from any residual nuclear reactions in the active portion. n

An auxiliary coolant loop 138 is provided to cool the blanket annular tank 106, the thermal shield 120, and the pressure vessel 28. This heat is removed by the water coolant 26 llowing downward through the annuli provided at the'outer surface of the reactor vessel, between the annularl tank `106 and the thermal shield 120 land around the outer surface of the thermal shield. The water is drawn through apertures 140, chamber 54, and outlets 50, through pipe means 142 and blanket coolant heat exchanger 144, through pipe means 145 to the auxiliary system heat exchanger 146, wherein the heat is rremovedtrom the water coolant and distributed to the atmosphere by conventional means. The coolant flows fromthe discharge end of the heat exchanger '146 by means of the pipe 148, to the intake Iof the auxiliary coolant pump 150 which feeds the coolant back into the tank 22 by means of the pipe 152. In the particular reactor described, a 430 gallon per minute capacity auxiliary cooling pump is used to llow water through the various annuli at a Velocity of between 3.5 to 5.5 per second, the entrance temperature of the water to the annuli being approximately F., the mixed mean exit temperature being approximately F.

The lluid in the blanket annularr tank 106 is cooled by a separate loop 154 wherein the fluid is removed from the annular tank 106 through pipe 110 and transmitted to the heat exchanger 144. The heat is removed from the blanket uid by the water coolant of the auxiliary loop 138 which llows therethrough as previously described. From 4the heat exchanger 144, the blanket fluid goes to the suction end of the blanket uid pump, 156 and thence back to the annular tank 106 through pipe 112. To maintain a blanket fluid temperature below the maximum limit of 180 F. and within a normal operating range of F. to 160 F., a 150 gallon per minute capacity pump is used. The total volume of blanket fluid in the loop 154 is approximately .7 cubic feet.

IRRADIATION SYSTEM The fluid in the blanket 106 is used to irradiate the selected materials by pumping it through specially designed irradiators a through 160), andv returned to the blanket. The irradiation iluid is withdrawn from the blanket 106 by means of tube 161 and distributed to the suction side of the pumps 162. The fluid is forced through the irradiators 160:1 through 160f and returned to the blanket tank 106 through pipe means 164.

We have discovered that an aqueous indium sulphate solution of up to 600 gms. per liter concentration using indiumV115 is ideal for use as the blanket fluid in a circulatory system with a neutronic reactor because of the relatively high absorption cross section for thermal neutrons of barns and the moderately short 54 minute half-life of the radioactive isotope indium 115. Indium 115 also emits an ideally suited spectrum of gamma energies while the moderating properties of the water in the solutionvadapt the fluid for utilizing the fast neutrons escaping the active portion into the blanket. The pumps n lirradiating can-packed materials` and are: readily shown in Figures through `8 of the drawings; The drum irra` diator comprises` a hexagonal drum 166 having parallel f Any inlet manifold 170 is provided near `the topv of the drum 166 for the irradiating duidA and a manifold'outlet 172 is disposed near the bottom for removal `of the uid. Withinthe drum 166 are baie plates 174 having apertures 176 thereinfor receiving the tubes 168' and are shaped to conform to the cross section of the drum 166 except for one shortened side 178 which permits the ow of fluid downward to the next level `foi'ined by a baille plate 174 immediately below.' The bafeplates 174 are arranged so that the short sides-'178 are alternately disposed adjacent `to oppositesides'of the hexagonaly drum 166 causing the uid to dow back and forth across the drum 166 as it ows from the inlet y170 down periphery of the drum 166 to give it needed support.

` Within the tubes 168 are can guides 182 spaced from saidY tubes 168 and having flutes 184'so lthat cans 186 are' spaced from said guides. A cooling fluid may thus be introduced into the'space between `the can andthe can guide to maintain the material in the cansat a desired temperature, the space between the can guide and th y a hexagonal drum measuring 39.66" across parallel sides.

The No. can irradiator 160b has l9 paralleltubes 168 measuring approximately 61" long for stacking ten cans, the drum measuring 38.3 across parallel sides.

yA drum radiator' installation is shown in Figure 5 `whereinthe drum radiator 160a is disposed within a cubical 188 formedby the radiation shield 190. A can carrier 192 is transportable between the` cubical 188 and a space 193 formed between the radiator shield 190 and an auxiliary shield wall 194 through passageway 196 whereby the cans of material to be irradiated may be introduced to a position below the drum radiator 160e. A passageway 198 is located in the auxiliary shield wall 194 at a level above the primary shield passageway 196 through which a can loading pallet `200 may be moved from the can loading position 201 outside of the shield wall 194 into a position within the shielded space 193 where the cans may be transferred to the can carrier 192. The cans are loaded into the can-loadinglpallet 200 in an array corresponding to the disposition of the tubes 168 in the drum irradiator 160:1 and moved into the space between the primary shield 190 andthe shield wall 194 where a can-loading mechanism 202 lowers the cans unto the can carrier 192 without disturbing the array. 'I'lie can carrier 192 is then transported into the cubical 188 below the drum irradiator 160a where suitable piston means 204 raise the cans into the tubes 168 where they are held in place by spring loaded pawls 206. Eachload of cans introduced into the bottom of the drum `irijadiatoi 160:1 forces the cans within the irradiator one step up until they reach the top of the drum irradiator where `they are lifted therefrom by a magnetic pick-up headAA 208 and moved to position 210 within the primary shield 190 where they are released to a conveyor belt `212. `The belt 212 transports the irradiated cans to the Aspace 193 between the two shields 190 and 194 where they are deposited on a second conveyor belt 214 and carried outside the shielded space through the slot 216. Access to the cubical 188 is had by removing the shield slabs 217 above the drum irradiator for'any necessary servicing. A similar irradiation facility'is used for irradiating No. ml0 `size cans in the drum irradiator 1462b j l tubes 168 disposed therethroughin a triangular'lattice;

iA"slabtype irradiatol.' k,useful `forfirradiating"A selected materials in odd and varied -shapesisshownin Figures 9.-=1Q. `The slab irradiator'160c is` constructedof 'a` series of U-shapechann'el members 218 assemblcdand welded,

as shown inFigure `10 with cover plates `220 closing the top and bottom ends of'the assembly. Each; of the channel members 218 has a large passageway222 at one end with a smaller passageway 224 at its other end,fthe channel; members 218 .being assembledso that alternate ones have theirk large passageways 222 at the upper end." "An inleta226 is provided near the ktop of one end of the irradiator 160,0 andan outlet 228 is located nearthe V2.0 toward the outlet 172. Stilefner ns 180 surround the f bottom of the oppositeend so that the irradiation'uid will flow in anup` `andi down path through` a slab irracliatoi'.`` A Y i flhe slabirradiator 1603, as'shown in' l1 through 13; is `designed primarily for irradiating selected matter packed in boxes and is essentially` fourirradiatorsysuch as m160e, stackediin layers 229., .and each having its own inlet 230 and outlet 232.` Each-layer229 comprises an assembly of welded U-shaped channel members\2/34havying larger and smaller passageways y23:6l and238.- respectively, atopposite ends ofthe channel members 234:0ppositely arranged ,soj that the-duid willow ,through the layers 229 in an essentially 'upand fdown path. Eachy layer 229 has its own upper and lower kplate cover 240 for closing the exposed rportions of the assembly.

The iiradiators 160C and 160f are merely straight tubes having diiferentL diameters to provide for low dose irradiations when other irradiators are in use with the reactor when it is operating at',relativelyyhighpower.y Theydo not have separate pumping means but lare designed :to operate off of thepump used for the slab irradiator C. `The particular reactor" described in this specication as oneembodimentof the invention has a designed maximum power rating of 20k megawatts, producing approxi mately 683x106 b.t;u./hr`. of heat. The normal operating `power of ythe reactor is k10.5 megawatts which makes available approximately 7 kilowatts'of gamma energy tok be absorbed in. the selected materials to be irradiated. The production rate of thesystem is 3000 lbs./hr.tirradi ated to a dosage of about 2X l06 rep (roentgen equivalent physical). The following table summarizes useful data forthe reactor system operating at the stated performance requirements: i t

Data summary Oore: i

' Equivalent diameter 1n 14.9 Heigli in 30 Volume in.a 6, 276 Metal-towater ratio (average) 0.7 Um content of new clean core.--` kg.- 11. 4 Cold, clean, critical mass (uranl kg.- 6.0 Power density (20 mw.) kw. 194. 5 Cold, clean, excess reactivity Percent AK/K- -12 Fuel Overall Core Enel Assemblies:

Fuel plates per assembly 16 Number of fuel assemblies 24 Uranium (9D-05% Um) per assembly grams 475 Metal-towater ratio O. 58 Control Rods: p t

Number- Shim-safety rods d Regulating rods Travelt A f Shim-safety rods in Regulating rods -..in Worth of shim-safety r p 4 blades, total. Porcent AK/K-- 8-1 l eruclform Percent AK/K-- 12-14h Heat transfer and fow data for 20 mim-operation Nominal operating pressure Coolant 'inlet temperature at reactor.- Coolant outlet temperature at reactor Total coolant dow through reactor- Number of passes in core--- Heat transfer area in core... Coolant low rate through c Coolant velocity through core Indzum systemy N o. 2 N o. 10 Cans Cans Drum Radiators:

Number 1 1 No. of tubes 61 19 15 10 915 190 1, 225 1, 310 Dwell time (3,0001b. r. min.- 24. 5 26. 2 Reactor power (3 ton-megareps/hr.) mw Y 10. 3 11. 6

Single-Slab Multiple-Slab Slab Radiators: v

Number 1 1 Number of units in radiator 1 4 Dimension of each unit slab..- 3 x 84 x 108 3 x 20 x 108 per unit No. of boxes 40 10 Weight of material in boxes (unit densit lb-- 2, 760 690 Dwell time (3,000 lb./hr.) min.' 55. 5 13. 9 Reactor power (3 ton-megarep/hr.)

terial, said portion having its length substantially greater than its diameter, a pressure Vessel enclosing the active portion, means for controlling the reactivity of said reactor, means for circulating a coolant through the pres-y sure vessel past the active portion, an annular tank surrounding and spaced from the pressure vessel around the active portion having a volume approximately equal to the volume of the active portion, la fluid within said tank comprising an aqueous indium115 sulphate solution of approximately 600 grams per liter concentration, a concrete shield having a reservoir containing said reactor, a second coolant disposed within the reservoir and covering the reactor, means for circulating said second coolant through the space between the annular tank and the pressure vessel; radiator means adapted to receive the selected materials, meansv for flowing said indium sulphate solution from said tank to said radiator means at a ow rate of -at least 15 gallons per minute whereby the selected materials are subjected to radioactive emissions released by said solution, means for returning said solution to said reservoir, and means for cooling a portion of said vindium sulfate solution comprising heat exchange means and means for owing a portion of said solution from said tank to the heat exchange means and returning the solution to the tank.

References Cited in the tile of this patent UNITED STATES PATENTS 2,708,656 Fermi et al. May 17, 1955 2,743,225 Ohlinger et al Apr. 24, 1956 2,815,321 Wigner et al. Dec. 3, 19'57 2,860,093

OTHER REFERENCES Brownell et al.: T.I.D.8002, Jan. 1956, :Technical lnv formationy Service, Atomic Energy Commission, Washington 25 D.C., pp. 1-3. n

Siuet al.: Vol. l5 of 'Proceedings of the International Conference on the APeaceful Uses of Atomic'Energy, United Nations, New York, 1956, page 271'.

Wigner et al. Nov. ll, 1958 

